The present invention relates to a method of manufacturing a chip-type aluminum electrolytic capacitor and, more particularly, to a method of manufacturing a chip-type aluminum electrolytic capacitor in which a flat capacitor element is packaged integrally with a synthetic resin laminate film and has a very small capacitance and small size and weight.
In a conventional chip-type aluminum electrolytic capacitor of the type described above, anode and cathode foils having anode and cathode lead wires connected thereto are cylindrically wound through an insulating spacer to form the capacitor element. The capacitor element is stored in a synthetic resin case with impregnation holes. An electrolytic solution is injected through the impregnation holes and thereafter the holes are closed. External leads are connected to the anode and cathode lead wires. The case is encapsulated in a synthetic resin capsule while the respective external leads are exposed.
In another conventional chip-type aluminum electrolytic capacitor, a capacitor element similarly obtained by cylindrically winding anode and cathode foils through an insulating spacer is housed in a cylindrical aluminum case. After impregnation with an electrolytic solution, the opening of the case is sealed with a rubber stopper. External leads are welded to anode and cathode lead wires. The case and the rubber stopper are encapsulated in a synthetic resin capsule while the external terminals are exposed.
However, with the chip-type aluminum electrolytic capacitor manufactured by the former method, the anode and cathode foils are wound through an insulating spacer. Therefore, the outer shape becomes cylindrical and the thickness of the chip-type aluminum electrolytic capacitor after forming a synthetic resin capsule is increased. In this case, according to one method, after anode and cathode foils are cylindrically wound through an insulating spacer, the obtained assembly is pressed into a flat shape. After impregnating the flat assembly with an electrolytic solution, it is encapsulated in a synthetic resin capsule. However, even with this method, the thickness of the capacitor after forming the capsule cannot be decreased beyond a certain extent. Thus, since the conventional chip-type aluminum electrolytic capacitor has a large thickness, the overall volume is increased. Therefore, the conventional chip-type aluminum electrolytic capacitor cannot be rendered lightweight and compact. In addition in the conventional chip-type aluminum electrolytic capacitor described above, since the electrode foils are wound cylindrically, they must have a certain length. That is, the length of the electrode foils cannot be reduced below a minimum limit required for the cylindrical winding operation. When the chip-type aluminum electrolytic capacitor must satisfy ratings for a low-voltage and small-capacitance capacitor, the formation voltage of the anode foil is intentionally increased to increase the area of the electrode foil, thereby making the winding operation easier. According to this method of manufacturing a chip-type aluminum electrolytic capacitor, the minimum size, length or weight that can be achieved is limited.
In addition to the conventional chip-type aluminum electrolytic capacitors described above, after electrode foils and an insulating spacer are cylindrically wound, the assembly is pressed flat. After impregnating the pressed assembly with an electrolytic solution, it is covered with a synthetic resin laminate film and the lead wires are left exposed. The laminate film is melted and sealed by heating or ultrasonic welding so as to provide a chip-type aluminum electrolytic capacitor. However, with this conventional method, since the electrode foils and the insulating spacer are cylindrically wound and thereafter the assembly is pressed flat, similar problems are encountered as with the former methods. The minimum size attainable with this method is 6 mm.times.6 mm.times.2.5 mm. A smaller and thinner capacitor element cannot be obtained.